The broad goal of this project is to achieve an understanding of the linguistic and non-linguistic factors that are associated with persistent deficits or successful recovery from initial language delay in a population of children who are in the bottom 10th percentile for expressive vocabulary between 18 and 24 months of age. To uncover the factors associated with early and persistent language delay, cross- sectional and longitudinal studies using experimental measures have been designed around two periods of development: (a) the earliest stages of language acquisition (18-36 months), when accurate determination of language impairment is still difficult to make, and (b) preschool to first grade (3-6 years), when diagnosis with standardized tests is possible. Hypotheses focus on (1) intralinguistic factors (e.g. receptive language profiles) that distinguish between "late bloomers: and the truly language impaired children during the "preclinical" stage (18- 24 months), and (2) extralinguistic factors (e.g. aspects of symbolic gesture) that also differentiate between these two groups, increasing the validity and reliability of early diagnosis. In addition, the shape and nature of recovery from delay in those children who do recover will be investigated including (3) cognitive infrastructures (non-linguistic skills that must be in place before successful recovery can begin), and (4) alternative methods of communication (gestural, vocal, facial) that differentiate "late bloomers" from children with persistent deficits. For those children who do show apparent recovery, the 3-6 year battery contains a series of more subtle linguistic measures that can be used to determine (5) whether or not "late bloomers" continue to display subtle deficits in oral language ability that may affect their performance in the school system. The behavioral profiles obtained in this project will be (6) coordinated with electrophysiological studies of the same children (project 5), to determine whether, and to what extend changes in linguistic and non-linguistic ability in late talkers can be linked to specific changes in brain organization for language. Finally, results for late talkers will be compared with the cross-domain profiles and developmental trajectories displayed by other groups (children with focal brain injury, Downs syndrome, and Williams syndrome) and normal controls under study within the Program Project. Students will be directly integrated into the research. They will each have individual projects, but will also learn by interacting with others in my lab at SDSU and in group lab meetings. They will also have opportunities to interact with other members of the Program Project research team from SDSU, UCSD, and the Salk Institute. Each student will meet regularly with the P.I.